Collect a sample from the suspected food, surface, water, or clinical specimen
Keep the sample refrigerated and transport it promptly to a laboratory
Perform culture on selective media for Listeria
Incubate under appropriate conditions and check for characteristic colony growth
Confirm suspected colonies with biochemical tests or MALDI-TOF
Use PCR or qPCR to detect Listeria DNA
Use immunoassays or rapid lateral flow tests for screening
For clinical cases, test blood, cerebrospinal fluid, or other relevant specimens
Perform serotyping or whole-genome sequencing for definitive identification and outbreak tracing
Follow laboratory biosafety and quality-control procedures throughout testing